Speech synthesizer using artificial intelligence, method of operating speech synthesizer and computer-readable recording medium

ABSTRACT

A speech synthesizer using artificial intelligence includes a memory, a communication unit for receiving utterance information of words uttered by a user, and a processor for acquiring a plurality of utterance intonation phrase (IP) ratios respectively corresponding to a plurality of words uttered by the user based on the utterance information, acquiring a plurality of non-utterance IP ratios respectively corresponding to a plurality of unuttered words based on the utterance information and the plurality of utterance IP ratios, and generating a personalized synthesized speech model based on the plurality of utterance IP ratios and the plurality of non-utterance IP ratios. A plurality of classes indicating reading break of a word includes first to third classes. A minor class has a smallest count among the first to third classes. Each of the utterance and non-utterance IP ratios is a ratio in which a word is classified as the minor class.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2019/007322, filed on Jun. 18, 2019, the contents of which are hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a speech synthesizer and, more particularly, to a speech synthesizer capable of improving reading break prediction performance.

BACKGROUND ART

Competition for speech recognition technology which has started in smartphones is expected to become fiercer in the home with diffusion of the Internet of things (IoT).

In particular, an artificial intelligence (AI) device capable of issuing a command using speech and having a talk is noteworthy.

A speech recognition service has a structure for selecting an optimal answer to a user's question using a vast amount of database.

A speech search function refers to a method of converting input speech data into text in a cloud server, analyzing the text and retransmitting a real-time search result to a device.

The cloud server has a computing capability capable of dividing a large number of words into speech data according to gender, age and intonation and storing and processing the speech data in real time.

As more speech data is accumulated, speech recognition will be accurate, thereby achieving human parity.

Recently, services for providing a synthesized speech in specific speaker's voice using a synthesized speech model have appeared.

For reading break learning of the synthesized speech model, a training set including one sentence (training data) and labeling data for labeling words configuring the sentence with reading break is required.

The reading break may be classified into first reading break, second reading break greater than the first reading break and third reading break greater than the second reading break.

When data having imbalance such as the count of specific reading break less than that of other reading break is used upon outputting the synthesized speech of one sentence, performance of the synthesized speech model may deteriorate.

In addition, in an existing synthesized speech model, only a uniformly synthesized speech in which words are read with break according to the utterance style of a specific voice actor without considering the utterance style of a user was provided. Therefore, sometimes, the user may feel uncomfortable when listening to the synthesized speech.

DISCLOSURE Technical Problem

Another object of the present invention is to provide a speech synthesizer capable of improving reading break prediction performance using artificial intelligence when a synthesized speech is output.

Another object of the present invention is to provide a speech synthesizer capable of outputting a synthesized speech optimized for a reading break style of a person using artificial intelligence.

Technical Solution

A speech synthesizer using artificial intelligence according to an embodiment of the present invention includes a memory, a communication unit configured to receive utterance information of words uttered by a user from a terminal, and a processor configured to acquire a plurality of utterance intonation phrase (IP) ratios respectively corresponding to a plurality of words uttered by the user based on the utterance information, acquire a plurality of non-utterance IP ratios respectively corresponding to a plurality of unuttered words based on the utterance information and the plurality of utterance IP ratios, and generate a personalized synthesized speech model based on the plurality of utterance IP ratios and the plurality of non-utterance IP ratios. A plurality of classes indicating reading break of a word includes a first class corresponding to first reading break, a second class corresponding to second reading break greater than the first break and a third class corresponding to third reading break greater than the second break, wherein a minor class has a smallest count among the first to third classes, and each of the utterance IP ratios and the non-utterance IP ratios is a ratio in which a word is classified as the minor class.

Advantageous Effects

According to the embodiment of the present invention, as performance of a synthesized speech model is improved, it is possible to naturally output a synthesized speech. Therefore, a listener may not feel uncomfortable when listening to the synthesized speech.

According to the embodiment of the present invention, as a personalized synthesized speech model is provided, a synthesized speech suiting the utterance style of a user is output, thereby improving user's satisfaction with a speech recognition service.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a terminal according to the present invention.

FIG. 2 is a diagram illustrating a speech system according to an embodiment of the present invention.

FIG. 2 is a view illustrating the concept of another example of a deformable mobile terminal according to the present invention.

FIG. 3 is a diagram illustrating a process of extracting utterance features of a user from a speech signal according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of converting a speech signal into a power spectrum according to an embodiment of the present invention.

FIG. 5 is a block diagram illustrating the configuration of a speech synthesis server according to an embodiment of the present invention.

FIGS. 6 and 7 are views illustrating a class imbalance problem when reading break is predicted through a conventional synthesized speech.

FIG. 8 is a flowchart illustrating a method of operating a speech synthesis server according to an embodiment of the present invention.

FIG. 9 is a flowchart illustrating a process of performing data augmentation of a word based on prior information according to an embodiment of the present invention.

FIG. 10 is a view showing an IP frequency number and a non-IP frequency number of each word stored in a database according to an embodiment of the present invention.

FIG. 11 is a view illustrating an oversampling rate determined according to a ratio of a non-IP frequency number to an IP frequency number.

FIG. 12 is a ladder diagram illustrating a method of operating a system according to an embodiment of the present invention.

FIG. 13 is a view illustrating a basic structure of a recurrent neural network.

FIG. 14 is a view illustrating a process of classifying words configuring a sentence into classes using a synthesized speech model according to an embodiment of the present invention.

FIG. 15 is a flowchart illustrating a method of operating a speech synthesis server using artificial intelligence according to another embodiment of the present invention.

FIG. 16 is a diagram illustrating prior information of each word stored in a database according to an embodiment of the present invention.

FIG. 17 is a diagram illustrating an example of a synthesized speech model according to an embodiment of the present invention.

FIGS. 18 to 21 are diagrams illustrating an example of correcting a class classification probability set in consideration of an IP ratio and a non-IP ratio of a word according to an embodiment of the present invention.

FIG. 22 is a diagram illustrating a process of learning a synthesized speech model using a newly acquired second class classification probability set based on an IP ratio according to an embodiment of the present invention.

FIG. 23 is a ladder diagram illustrating a method of operating another system of the present invention.

FIG. 24 is a view illustrating a plurality of IP tables respectively corresponding to a plurality of voice actors according to an embodiment of the present invention.

FIG. 25 is a view illustrating a normal IP ratio table according to an embodiment of the present invention.

FIG. 26 is a view illustrating a table including personalized IP ratios and normal IP ratios of acquired words based on utterance information of a user.

FIG. 27 is a view illustrating an IP ratio model according to an embodiment of the present invention.

FIG. 28 is a view illustrating a result of estimating personalized IP ratios of words unuttered by a user according to an embodiment of the present invention.

FIG. 29 is a flowchart illustrating a process of updating a personalized synthesized speech model at a speech synthesizer according to an embodiment of the present invention.

BEST MODE

Description will now be given in detail according to exemplary embodiments disclosed herein, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components may be provided with the same reference numbers, and description thereof will not be repeated. In general, a suffix such as “module” or “unit” may be used to refer to elements or components. Use of such a suffix herein is merely intended to facilitate description of the specification, and the suffix itself is not intended to have any special meaning or function. In the present disclosure, that which is well-known to one of ordinary skill in the relevant art has generally been omitted for the sake of brevity. The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings.

While ordinal numbers including ‘first’, ‘second’, etc. may be used to describe various components, they are not intended to limit the components. These expressions may be used to distinguish one component from another component

When it is said that a component is ‘coupled with/to’ or ‘connected to’ another component, it should be understood that the one component is connected to the other component directly or through any other component in between. On the other hand, when it is said that a component is ‘directly connected to’ or ‘directly coupled to’ another component, it should be understood that there is no other component between the components.

The terminal described in this specification may include cellular phones, smart phones, laptop computers, digital broadcast terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigators, portable computers (PCs), slate PCs, tablet PCs, ultra books, wearable devices (for example, smart watches, smart glasses, head mounted displays (HMDs)), and the like.

However, the artificial intelligence device 100 described in this specification is applicable to stationary terminals such as smart TVs, desktop computers or digital signages.

In addition, the terminal 100 according to the embodiment of the present invention is applicable to stationary or mobile robots.

In addition, the terminal 100 according to the embodiment of the present invention may perform the function of a speech agent. The speech agent may be a program for recognizing the speech of a user and audibly outputting a response suitable to the recognized speech of the user.

The terminal 100 may include a wireless communication unit 110, an input unit 120, a learning processor 130, a sensing unit 140, an output unit 150, an interface 160, a memory 170, a processor 180 and a power supply 190.

The wireless communication unit 110 may include at least one of a broadcast reception module 111, a mobile communication module 112, a wireless Internet module 113, a short-range communication module 114 and a location information module 115.

The broadcast reception module 111 receives broadcast signals and/or broadcast associated information from an external broadcast management server through a broadcast channel.

The mobile communication module 112 may transmit and/or receive wireless signals to and from at least one of a base station, an external terminal, a server, and the like over a mobile communication network established according to technical standards or communication methods for mobile communication (for example, Global System for Mobile Communication (GSM), Code Division Multi Access (CDMA), CDMA2000 (Code Division Multi Access 2000), EV-DO (Enhanced Voice-Data Optimized or Enhanced Voice-Data Only), Wideband CDMA (WCDMA), High Speed Downlink Packet access (HSDPA), HSUPA (High Speed Uplink Packet Access), Long Term Evolution (LTE), LTE-A (Long Term Evolution-Advanced), and the like).

The wireless Internet module 113 is configured to facilitate wireless Internet access. This module may be installed inside or outside the terminal 100. The wireless Internet module 113 may transmit and/or receive wireless signals via communication networks according to wireless Internet technologies.

Examples of such wireless Internet access include Wireless LAN (WLAN), Wireless Fidelity (Wi-Fi), Wi-Fi Direct, Digital Living Network Alliance (DLNA), Wireless Broadband (WiBro), Worldwide Interoperability for Microwave Access (WiMAX), High Speed Downlink Packet Access (HSDPA), HSUPA (High Speed Uplink Packet Access), Long Term Evolution (LTE), LTE-A (Long Term Evolution-Advanced), and the like.

The short-range communication module 114 is configured to facilitate short-range communication and to support short-range communication using at least one of Bluetooth™, Radio Frequency IDentification (RFID), Infrared Data Association (IrDA), Ultra-WideBand (UWB), ZigBee, Near Field Communication (NFC), Wireless-Fidelity (Wi-Fi), Wi-Fi Direct, Wireless USB (Wireless Universal Serial Bus), and the like.

The location information module 115 is generally configured to acquire the position (or the current position) of the mobile terminal. Representative examples thereof include a Global Position System (GPS) module or a Wi-Fi module. As one example, when the terminal uses a GPS module, the position of the mobile terminal may be acquired using a signal sent from a GPS satellite.

The input unit 120 may include a camera 121 for receiving a video signal, a microphone 122 for receiving an audio signal, and a user input unit 123 for receiving information from a user.

Voice data or image data collected by the input unit 120 may be analyzed and processed as a control command of the user.

The input unit 120 may receive video information (or signal), audio information (or signal), data or user input information. For reception of video information, the terminal 100 may include one or a plurality of cameras 121.

The camera 121 may process image frames of still images or moving images obtained by image sensors in a video call more or an image capture mode. The processed image frames can be displayed on the display 151 or stored in memory 170.

The microphone 122 processes an external acoustic signal into electrical audio data. The processed audio data may be variously used according to function (application program) executed in the terminal 100. Meanwhile, the microphone 122 may include various noise removal algorithms to remove noise generated in the process of receiving the external acoustic signal.

The user input unit 123 receives information from a user. When information is received through the user input unit 123,

The processor 180 may control operation of the terminal 100 in correspondence with the input information.

The user input unit 123 may include one or more of a mechanical input element (for example, a mechanical key, a button located on a front and/or rear surface or a side surface of the terminal 100, a dome switch, a jog wheel, a jog switch, and the like) or a touch input element. As one example, the touch input element may be a virtual key, a soft key or a visual key, which is displayed on a touchscreen through software processing, or a touch key located at a location other than the touchscreen.

The learning processor 130 may be configured to receive, classify, store and output information to be used for data mining, data analysis, intelligent decision, mechanical learning algorithms and techniques.

The learning processor 130 may include one or more memory units configured to store data received, detected, sensed, generated or output in a predetermined manner or another manner by the terminal or received, detected, sensed, generated or output in a predetermined manner or another manner by another component, device, terminal or device for communicating with the terminal.

The learning processor 130 may include a memory integrated with or implemented in the terminal. In some embodiment, the learning processor 130 may be implemented using the memory 170.

Selectively or additionally, the learning processor 130 may be implemented using a memory related to the terminal, such as an external memory directly coupled to the terminal or a memory maintained in a server communicating with the terminal.

In another embodiment, the learning processor 130 may be implemented using a memory maintained in a cloud computing environment or another remote memory accessible by the terminal through the same communication scheme as a network.

The learning processor 130 may be configured to store data in one or more databases in order to identify, index, categorize, manipulate, store, retrieve and output data to be used for supervised or unsupervised learning, data mining, predictive analysis or other machines.

Information stored in the learning processor 130 may be used by one or more other controllers of the terminal or the processor 180 using any one of different types of data analysis algorithms and machine learning algorithms.

Examples of such algorithms include k-nearest neighbor systems, fuzzy logic (e.g., possibility theory), neural networks, Boltzmann machines, vector quantization, pulse neural networks, support vector machines, maximum margin classifiers, hill climbing, inductive logic system Bayesian networks, Petri Nets (e.g., finite state machines, Mealy machines or Moore finite state machines), classifier trees (e.g., perceptron trees, support vector trees, Marcov trees, decision tree forests, random forests), betting models and systems, artificial fusion, sensor fusion, image fusion, reinforcement learning, augmented reality, pattern recognition, and automated planning.

The processor 180 may make a decision using data analysis and machine learning algorithms and determine or predict at least one executable operation of the terminal based on the generated information. To this end, the processor 180 may request, retrieve, receive or use the data of the processor 130 and control the terminal to execute preferable operation or predicted operation of at least one executable operation.

The processor 180 may perform various functions for implementing intelligent emulation (that is, a knowledge based system, an inference system and a knowledge acquisition system). This is applicable to various types of systems (e.g., a fussy logic system) including an adaptive system, a machine learning system, an artificial neural system, etc.

The processor 180 may include a sub module for enabling operation involving speech and natural language speech processing, such as an I/O processing module, an environmental condition module, speech-to-text (STT) processing module, a natural language processing module, a workflow processing module and a service processing module.

Each of such sub modules may have an access to one or more systems or data and models at the terminal or a subset or superset thereof. In addition, each of the sub modules may provide various functions including vocabulary index, user data, a workflow model, a service model and an automatic speech recognition (ASR) system.

In another embodiment, the other aspects of the processor 180 or the terminal may be implemented through the above-described sub modules, systems or data and models.

In some embodiments, based on the data of the learning processor 130, the processor 180 may be configured to detect and sense requirements based on the context condition or user's intention expressed in user input or natural language input.

The processor 180 may actively derive and acquire information necessary to fully determine the requirements based on the context condition or user's intention. For example, the processor 180 may actively derive information necessary to determine the requirements, by analyzing historical data including historical input and output, pattern matching, unambiguous words, and input intention, etc.

The processor 180 may determine a task flow for executing a function for responding to the requirements based on the context condition or the user's intention.

The processor 180 may be configured to collect, sense, extract, detect and/or receive signals or data used for data analysis and machine learning operations through one or more sensing components at the terminal, in order to collect information for processing and storage from the learning processor 130.

Information collection may include sensing information through a sensor, extracting information stored in the memory 170, or receiving information from another terminal, an entity or an external storage device through a communication unit.

The processor 180 may collect and store usage history information from the terminal.

The processor 180 may determine the best match for executing a specific function using the stored usage history information and predictive modeling.

The processor 180 may receive or sense surrounding environment information or other information through the sensing unit 140.

The processor 180 may receive broadcast signals and/or broadcast related information, wireless signals or wireless data through the wireless communication unit 110.

The processor 180 may receive image information (or signals corresponding thereto), audio signal (or signals corresponding thereto), data or user input information from the input unit 120.

The processor 180 may collect information in real time, process or classify the information (e.g., a knowledge graph, a command policy, a personalization database, a dialog engine, etc.), and store the processed information in the memory 170 or the learning processor 130.

When the operation of the terminal is determined based on data analysis and machine learning algorithms and techniques, the processor 180 may control the components of the terminal in order to execute the determined operation. The processor 180 may control the terminal according to a control command and perform the determined operation.

When the specific operation is performed, the processor 180 may analyze historical information indicating execution of the specific operation through data analysis and machine learning algorithms and techniques and update previously learned information based on the analyzed information.

Accordingly, the processor 180 may improve accuracy of future performance of data analysis and machine learning algorithms and techniques based on the updated information, along with the learning processor 130.

The sensing unit 140 may include one or more sensors configured to sense internal information of the mobile terminal, the surrounding environment of the mobile terminal, user information, and the like.

For example, the sensing unit 140 may include at least one of a proximity sensor, an illumination sensor, a touch sensor, an acceleration sensor, a magnetic sensor, a G-sensor, a gyroscope sensor, a motion sensor, an RGB sensor, an infrared (IR) sensor, a finger scan sensor, an ultrasonic sensor, an optical sensor (for example, a camera 121), a microphone 122, a battery gauge, an environment sensor (for example, a barometer, a hygrometer, a thermometer, a radiation detection sensor, a thermal sensor, and a gas sensor), and a chemical sensor (for example, an electronic nose, a health care sensor, a biometric sensor, and the like). The mobile terminal disclosed in this specification may be configured to combine and utilize information obtained from at least two sensors of such sensors.

The output unit 150 is typically configured to output various types of information, such as audio, video, tactile output, and the like. The output unit 150 may include a display 151, an audio output module 152, a haptic module 153, and a light output unit 154.

The display 151 is generally configured to display (output) information processed in the terminal 100. For example, the display 151 may display execution screen information of an application program executed by the terminal 100 or user interface (UI) and graphical user interface (GUI) information according to the executed screen information.

The display 151 may have an inter-layered structure or an integrated structure with a touch sensor in order to realize a touchscreen. The touchscreen may provide an output interface between the terminal 100 and a user, as well as function as the user input unit 123 which provides an input interface between the terminal 100 and the user.

The audio output module 152 is generally configured to output audio data received from the wireless communication unit 110 or stored in the memory 170 in a call signal reception mode, a call mode, a record mode, a speech recognition mode, a broadcast reception mode, and the like.

The audio output module 152 may also include a receiver, a speaker, a buzzer, or the like.

A haptic module 153 can be configured to generate various tactile effects that a user feels. A typical example of a tactile effect generated by the haptic module 153 is vibration.

A light output unit 154 may output a signal for indicating event generation using light of a light source of the terminal 100. Examples of events generated in the terminal 100 may include message reception, call signal reception, a missed call, an alarm, a schedule notice, email reception, information reception through an application, and the like.

The interface 160 serves as an interface with external devices to be connected with the terminal 100. The interface 160 may include wired or wireless headset ports, external power supply ports, wired or wireless data ports, memory card ports, ports for connecting a device having an identification module, audio input/output (I/O) ports, video I/O ports, earphone ports, or the like. The terminal 100 may perform appropriate control related to the connected external device in correspondence with connection of the external device to the interface 160.

The identification module may be a chip that stores a variety of information for granting use authority of the terminal 100 and may include a user identity module (UIM), a subscriber identity module (SIM), a universal subscriber identity module (USIM), and the like. In addition, the device having the identification module (also referred to herein as an “identifying device”) may take the form of a smart card. Accordingly, the identifying device can be connected with the terminal 100 via the interface 160.

The memory 170 stores data supporting various functions of the terminal 100.

The memory 170 may store a plurality of application programs or applications executed in the terminal 100, data and commands for operation of the terminal 100, and data for operation of the learning processor 130 (e.g., at least one piece of algorithm information for machine learning).

The processor 180 generally controls overall operation of the terminal 100, in addition to operation related to the application program. The processor 180 may process signals, data, information, etc. input or output through the above-described components or execute the application program stored in the memory 170, thereby processing or providing appropriate information or functions to the user.

In addition, the processor 180 may control at least some of the components described with reference to FIG. 1 in order to execute the application program stored in the memory 170. Further, the processor 180 may operate a combination of at least two of the components included in the terminal 100, in order to execute the application program.

The power supply 190 receives external power or internal power and supplies the appropriate power required to operate respective components included in the terminal 100, under control of the controller 180. The power supply 190 may include a battery, and the battery may be a built-in or rechargeable battery.

Meanwhile, as described above, the processor 180 controls operation related to the application program and overall operation of the terminal 100. For example, the processor 180 may execute or release a lock function for limiting input of a control command of the user to applications when the state of the mobile terminal satisfies a set condition.

FIG. 2 is a diagram illustrating a speech system according to an embodiment of the present invention.

Referring to FIG. 2, the speech system 1 includes an terminal 100, a speech-to-text (STT) server 10, a natural language processing (NLP) server 20 and a speech synthesis server 30.

The terminal 100 may transmit speech data to the STT server 10.

The STT server 10 may convert the speech data received from the terminal 100 into text data.

The STT server 10 may increase accuracy of speech-text conversion using a language model.

The language model may mean a model capable of calculating a probability of a sentence or a probability of outputting a next word is output when previous words are given.

For example, the language model may include probabilistic language models such as a unigram model, a bigram model, an N-gram model, etc.

The unigram model refers to a model that assumes that use of all words is completely independent of each other and calculates the probability of a word string by a product of the probabilities of words.

The bigram model refers to a model that assumes that use of words depends on only one previous word.

The N-gram model refers to a model that assumes that use of words depends on (n−1) previous words.

That is, the STT server 10 may determine when the speech data is appropriately converted into the text data using the language model, thereby increasing accuracy of conversion into the text data.

The NLP server 20 may receive the text data from the STT server 10. The NLP server 20 may analyze the intention of the text data based on the received text data.

The NLP server 20 may transmit intention analysis information indicating the result of performing intention analysis to the terminal 100.

The NLP server 20 may sequentially perform a morpheme analysis step, a syntax analysis step, a speech-act analysis step, a dialog processing step with respect to text data, thereby generating intention analysis information.

The morpheme analysis step refers to a step of classifying the text data corresponding to the speech uttered by the user into morphemes as a smallest unit having a meaning and determining the part of speech of each of the classified morphemes.

The syntax analysis step refers to a step of classifying the text data into a noun phrase, a verb phrase, an adjective phrase, etc. using the result of the morpheme analysis step and determines a relation between the classified phrases.

Through the syntax analysis step, the subject, object and modifier of the speech uttered by the user may be determined.

The speech-act analysis step refers to a step of analyzing the intention of the speech uttered by the user using the result of the syntax analysis step. Specifically, the speech-act step refers to a step of determining the intention of a sentence such as whether the user asks a question, makes a request, or expresses simple emotion.

The dialog processing step refers to a step of determining whether to answer the user's utterance, respond to the user's utterance or question about more information.

The NLP server 20 may generate intention analysis information including at least one of the answer to, a response to, or a question about more information on the intention of the user's utterance, after the dialog processing step.

Meanwhile, the NLP server 20 may receive the text data from the terminal 100. For example, when the terminal 100 supports the speech-to-text conversion function, the terminal 100 may convert the speech data into the text data and transmit the converted text data to the NLP server 20.

The speech synthesis server 30 may synthesize prestored speech data to generate a synthesized speech.

The speech synthesis server 30 may record the speech of the user selected as a model and divide the recorded speech into syllables or words. The speech synthesis server 30 may store the divided speech in an internal or external database in syllable or word units.

The speech synthesis server 30 may retrieve syllables or words corresponding to the given text data from the database and synthesize the retrieved syllables or words, thereby generating the synthesized speech.

The speech synthesis server 30 may store a plurality of speech language groups respectively corresponding to a plurality of languages.

For example, the speech synthesis server 30 may include a first speech language group recorded in Korean and a second speech language group recorded in English.

The speech synthesis server 30 may translate text data of a first language into text of a second language and generate a synthesized speech corresponding to the translated text of the second language using the second speech language group.

The speech synthesis server 30 may transmit the synthesized speech to the terminal 100.

The speech synthesis server 30 may receive the intention analysis information from the NLP server 20.

The speech synthesis server 30 may generate the synthesized speech including the intention of the user based on the intention analysis information.

In one embodiment, the STT server 10, the NLP server 20 and the speech synthesis server 30 may be implemented as one server.

The respective functions of the STT server 10, the NLP server 20 and the speech synthesis server 30 may also be performed in the terminal 100. To this end, the terminal 100 may include a plurality of processors.

FIG. 3 is a diagram illustrating a process of extracting utterance features of a user from a speech signal according to an embodiment of the present invention.

The terminal 100 shown in FIG. 1 may further include an audio processor 181.

The audio processor 181 may be implemented as a chip separated from the processor 180 or a chip included in the processor 180.

The audio processor 181 may remove noise from the speech signal.

The audio processor 181 may convert the speech signal into text data. To this end, the audio processor 181 may include an STT engine.

The audio processor 181 may recognize a wake-up word for activating speech recognition of the terminal 100. The audio processor 181 may convert the wake-up word received through the microphone 121 into text data and determine that the wake-up word is recognized when the converted text data corresponds to the prestored wake-up word.

The audio processor 181 may convert the speech signal, from which noise is removed, into a power spectrum.

The power spectrum may be a parameter indicating a frequency component included in the waveform of the speech signal varying with time, and a magnitude thereof.

The power spectrum shows a distribution of an amplitude squared value according to the frequency of the waveform of the speech signal.

This will be described with reference to FIG. 4.

FIG. 4 is a diagram illustrating an example of converting a speech signal into a power spectrum according to an embodiment of the present invention.

Referring to FIG. 4, the speech signal 410 is shown. The speech signal 410 may be received through the microphone 121 or prestored in the memory 170.

The x-axis of the speech signal 410 denotes a time and the y-axis denotes an amplitude.

The audio processor 181 may convert the speech signal 410, the x-axis of which is a time axis, into a power spectrum 430, the x-axis of which is a frequency axis.

The audio processor 181 may convert the speech signal 410 into the power spectrum 430 using Fast Fourier transform (FFT).

The x-axis of the power spectrum 430 denotes a frequency and the y-axis of the power spectrum 430 denotes a squared value of an amplitude.

FIG. 3 will be described again.

The processor 180 may determine utterance features of a user using at least one of the power spectrum 430 or the text data received from the audio processor 181.

The utterance features of the user may include the gender of the user, the pitch of the user, the tone of the user, the topic uttered by the user, the utterance speed of the user, the volume of the user's voice, etc.

The processor 180 may acquire the frequency of the speech signal 410 and the amplitude corresponding to the frequency using the power spectrum 430.

The processor 180 may determine the gender of the user who utters a speech, using the frequency band of the power spectrum 430.

For example, the processor 180 may determine the gender of the user as a male when the frequency band of the power spectrum 430 is within a predetermined first frequency band range.

The processor 180 may determine the gender of the user as a female when the frequency band of the power spectrum 430 is within a predetermined second frequency band range. Here, the second frequency band range may be larger than the first frequency band range.

The processor 180 may determine the pitch of the speech using the frequency band of the power spectrum 430.

For example, the processor 180 may determine the pitch of the speech according to the amplitude within a specific frequency band range.

The processor 180 may determine the tone of the user using the frequency band of the power spectrum 430. For example, the processor 180 may determine a frequency band having a certain amplitude or more among the frequency bands of the power spectrum 430 as a main register of the user and determines the determined main register as the tone of the user.

The processor 180 may determine the utterance speed of the user through the number of syllables uttered per unit time from the converted text data.

The processor 180 may determine the topic uttered by the user using a Bag-Of-Word Model scheme with respect to the converted text data.

The Bag-Of-Word Model scheme refers to a scheme for extracting mainly used words based on the frequency of words in a sentence. Specifically, the Bag-Of-Word Model scheme refers to a scheme for extracting unique words from a sentence, expressing the frequency of the extracted words by a vector and determining the uttered topic as a feature.

For example, when words <running>, <physical strength>, etc. frequently appears in the text data, the processor 180 may classify the topic uttered by the user into an exercise.

The processor 180 may determine the topic uttered by the user from the text data using a known text categorization scheme. The processor 180 may extract keywords from the text data and determine the topic uttered by the user.

The processor 180 may determine the volume of user's voice in consideration of the amplitude information in an entire frequency band.

For example, the processor 180 may determine the volume of user's voice based on an average or weighted average of amplitudes in each frequency band of the power spectrum.

The functions of the audio processor 181 and the processor 180 described with reference to FIGS. 3 and 4 may be performed in any one of the NLP server 20 or the speech synthesis server 30.

For example, the NLP server 20 may extract the power spectrum using the speech signal and determine the utterance features of the user using the extracted power spectrum.

FIG. 5 is a block diagram illustrating the configuration of a speech synthesis server according to an embodiment of the present invention.

The speech synthesis server 30 is a device or server disposed outside the terminal 100 and may perform the same function as the learning processor 130 of the terminal 100.

That is, the speech synthesis server 30 may be configured to receive, classify, store and output information to be used for data mining, data analysis, intelligent decision, mechanical learning algorithms. Here, the machine learning algorithms may include a deep learning algorithm.

The speech synthesis server 30 may communicate with at least one terminal 100 and derive a result by analyzing or learning data instead of or in aid of the terminal 100. Aiding another device may mean distribution of computing power through distribution processing.

The speech synthesis server 30 is a variety of devices for learning an artificial neural network, may generally mean a server, and may be referred to as a learning device or a learning server.

In particular, the speech synthesis server 30 may be implemented not only as a single server but also as a plurality of server sets, a cloud server or a combination thereof.

That is, a plurality of speech synthesis servers 30 may configure a learning device set (or a cloud server) and at least one speech synthesis server 30 included in the learning device set may derive a result by analyzing or learning data through distribution processing.

The speech synthesis server 30 may transmit a model learned by machine learning or deep learning to the terminal 100 periodically or according to a request.

Referring to FIG. 5, the speech synthesis server 30 may include a communication unit 210, an input unit 220, a memory 230, a learning processor 240, a power supply 250 and a processor 260.

The communication unit 210 may correspond to a component including the wireless communication unit 110 and the interface 160 of FIG. 1. That is, data may be transmitted to and received from another device through wired/wireless communication or an interface.

The input unit 220 may correspond to the input unit 120 of FIG. 1 and acquire data by receiving data through the communication unit 210.

The input unit 220 may acquire input data for acquiring output using training data for model learning or a trained model.

The input unit 220 may acquire raw input data. In this case, the processor 260 may preprocess the acquired data to generate training data or preprocessed input data capable of being input to model learning.

At this time, preprocessing of the input data performed by the input unit 220 may mean extraction of input features from the input data.

The memory 230 may correspond to the memory 170 of FIG. 1.

The memory 230 may include a model storage unit 231 and a database 232.

The model storage unit 231 stores a model (or an artificial neural network 231 a) which is learned or being learned through the learning processor 240 and stores an updated model when the model is updated through learning.

At this time, the model storage unit 231 may classify and store the trained model into a plurality of versions according to a learning time point or learning progress, as necessary.

The artificial neural network 231 a shown in FIG. [[2]] 5 is merely an example of the artificial neural network including a plurality of hidden layers and the artificial neural network of the present invention is not limited thereto.

The artificial neural network 231 a may be implemented in hardware, software or a combination of hardware and software. When some or the whole of the artificial neural network 231 a is implemented in software, one or more commands configuring the artificial neural network 231 a may be stored in the memory 230.

The database 232 stores the input data acquired by the input unit 220, learning data (or training data) used for model learning, or a learning history of a model.

The input data stored in the database 232 may be not only data processed to suit model learning but also raw input data.

The learning processor 240 corresponds to the learning processor 130 of FIG. 1.

The learning processor 240 may train or learn the artificial neural network 231 a using training data or a training set.

The learning processor 240 may immediately acquire data obtained by preprocessing the input data acquired by the processor 260 through the input unit 220 to learn the artificial neural network 231 a or acquire the preprocessed input data stored in the database 232 to learn the artificial neural network 231 a.

Specifically, the learning processor 240 may determine the optimized model parameters of the artificial neural network 231 a, by repeatedly learning the artificial neural network 231 a using the above-described various learning schemes.

In this specification, the artificial neural network having parameters determined through learning using training data may be referred to as a training model or a trained model.

At this time, the training model may infer a result value in a state of being installed in the speech synthesis server 30 of the artificial neural network and may be transmitted to and installed in another device such as the terminal 100 through the communication unit 210.

In addition, when the training model is updated, the updated training model may be transmitted to and installed in another device such as the terminal 100 through the communication unit 210.

The power supply 250 corresponds to the power supply 190 of FIG. 1.

A repeated description of components corresponding to each other will be omitted.

FIGS. 6 and 7 are views illustrating a class imbalance problem when a reading break is predicted through a conventional synthesized speech.

FIG. 6 is a view showing a result of performing reading with break through a synthesized speech at a synthesized speech engine with respect to one sentence 600.

The synthesized speech engine may convert text into speech and output the speech.

The synthesized speech engine may be provided in the terminal 100 or the speech synthesis server 30.

A space bar 601 indicates that reading break is 1, </> 603 indicates that the reading break is 2 and <//>605 indicates that the reading break is 3.

The reading break may indicate a time interval when text is read. That is, as the reading break increases, the time interval when text is read may increase. In contrast, as the reading break decreases, the time interval when text is read may decrease.

FIG. 7 shows a class table 700 indicating a result of analyzing the reading break with respect to the sentence 600 of FIG. 6.

The class table 700 may include a word phrase (WP) class, an accentual phrase (AP) class and an intonation phrase (IP) class.

The word phrase class indicates that reading break is 1 and may indicate a class that words are read without break.

The accentual phrase class indicates that reading break is 2 and may indicate that break between words is small.

The intonation phrase class indicates that reading break is 3 and may indicate that break between words is large.

In the sentence 600 of FIG. 6, the count of word phrase classes is 7, the count of accentual phrase classes is 19 and the count of intonation phase classes is 4.

A class with a smallest count is called a minor class and a class with a largest count is called a major class.

In FIG. 7, the intonation phrase class may be the minor class and the accentual phrase class may be the major class.

When class imbalance in which the count of intonation phrase classes is less than the count of the other classes occurs, in a machine learning process of reading with break through a synthesized speech, the intonation phrase class may be determined as being less important and reading break performance of the synthesized speech model may deteriorate.

Specifically, for reading break learning of the synthesized speech model, a training set including one sentence (training data) and labeling data for labeling words configuring the sentence with reading breaks is required.

When data with class imbalance is used as labeling data, performance of the synthesized speech model may deteriorate.

When performance of the synthesized speech model deteriorates, reading with break may become unnatural when the synthesized speech is output and thus users may feel uncomfortable when listening to the synthesized speech.

In order to solve such a problem, in the present invention, the counts of classes are adjusted in a balanced way, thereby improving reading break prediction performance.

FIG. 8 is a flowchart illustrating a method of operating a speech synthesis server according to an embodiment of the present invention.

The processor 260 of the speech synthesis server 30 acquires prior information of each of a plurality of words corresponding to the minor class (S801).

Hereinafter, assume that the minor class is the intonation phrase class of FIG. 7.

A word belonging to (or being classified as) the intonation phrase class means that a word located before <//> indicating reading break of 3, such as <government's> shown in FIG. 6, belongs to the intonation phrase class.

In one embodiment, the prior information may include one or more of an intonation phrase (hereinafter referred to as IP) ratio of a word, an IP frequency number, a non-IP ratio, a non-IP frequency number, or a ratio of the non-IP frequency number to the IP frequency number.

The IP ratio may indicate a ratio in which a word is classified as the IP class, in the database 232. Specifically, in 10000 sentences in the database 232, when the number of times of classifying a first word into an IP class is 100, the IP ratio of the first word may be 1%(100/10000×100).

In the 10000 sentences, when the number of times of classifying a second word into the IP class is 200, the IP ratio of the second word may be 2%.

Of course, only some of the 10000 sentences may include the first word or the second word.

The IP frequency number may indicate the number of times of classifying a word into the IP class in the database 232. In the above example, the IP frequency number of the first word may be 100 and the IP frequency number of the second word may be 200.

The non-IP ratio may indicate a ratio of a word classified as a class other than the IP class in the database 232.

For example, in 10000 sentences of the database 232, when the number of times of classifying the first word into a class other than the IP class is 500, the non-IP ratio of the first word may be 5%(500/10000×100).

The non-IP frequency number may indicate the number of times in which the word is not classified as the IP class in the database 232.

For example, in 10000 sentences of the database, when the number of times in which the first word is not classified as the IP class is 300, the non-IP ratio of the first word may be 3%(300/10000×100).

The processor 260 of the speech synthesis server 30 performs data augmentation with respect to each data based on the acquired prior information (S803).

In one embodiment, data augmentation may be a process of increasing a frequency number in which a word belongs to a specific class in order to increase a probability that the word belongs to the specific class.

Increasing the frequency number in which the word belongs to the specific class may indicate that the number of sentences including the word belonging to the specific class increases.

This may be interpreted as increasing a training set for learning of the synthesized speech model.

This will be described in detail below.

The processor 260 of the speech synthesis server 30 stores a result of performing data augmentation in the database 232 (S805).

The processor 260 of the speech synthesis server 30 or the learning processor 240 performs machine learning for reading with break using the stored result of performing data augmentation (S807).

Machine learning for reading with break may be a process of determining with which break the words configuring a sentence is read when the sentence is input.

That is, machine learning for reading with break may be learning for classifying one sentence into a word phrase class, an accentual phrase class and an intonation phrase class.

A synthesized speech model may be generated according to machine learning for reading with break.

The synthesized speech model may refer to a model for receiving one sentence as input data and outputting synthesized speech data in which words configuring one sentence are classified into three optimized reading break classes.

The processor 260 of the speech synthesis server 30 may transmit the generated synthesized speech model to the terminal 100 through the communication unit 210.

FIG. 9 is a flowchart illustrating a process of performing data augmentation of a word based on prior information according to an embodiment of the present invention.

In particular, FIG. 9 is a view illustrating steps S803 and S805 shown in FIG. 8 in detail.

The processor 260 of the speech synthesis server 30 determines the oversampling rate of each word based on the prior information of the word (S901)

In one embodiment, the processor 260 may determine the oversampling rate of the word based on the ratio of the non-IP frequency number to the IP frequency number of the word classified as the minor class.

The oversampling rate may indicate a rate at which the word belongs to the IP class in the database 232.

The processor 260 may increase the oversampling rate as the ratio of the non-IP frequency number to the IP frequency number of the word increases.

The processor 260 may decrease the oversampling rate as the ratio of the non-IP frequency number to the IP frequency number of the word increases.

This will be described with reference to FIG. 10.

FIG. 10 is a view showing an IP frequency number and a non-IP frequency number of each word stored in a database according to an embodiment of the present invention.

FIG. 10 shows a result obtained by measuring reading break after uttering a specific word when a voice actor utters a large number of sentences, in order to generate a synthesized speech.

For example, assume that the frequency number in which a word <but> is classified as the IP class in the database 232 is 60 and the frequency number in which the word <but> is classified as the non-IP class instead of the IP class is 10.

Since the ratio of the non-IP frequency number to the IP frequency number is 1:6, the processor 260 may determine that the oversampling rate of the word <but> is 60% (6/1×0.1).

For example, the processor 260 may increase the existing frequency number, in which the word <but> is classified as the IP class, to 96 which is greater than 60 by 60%.

In another example, assume that the frequency number in which a word <can> is classified as the IP class in the database 232 is 30 and the frequency number in which the word <can> is classified as the non-IP class instead of the IP class is 120.

Since the ratio of the non-IP frequency number to the IP frequency number is 4:1, the processor 260 may determine that the oversampling rate of the word <can> is 2.5% (1/4×0.1).

For example, the processor 260 may increase the existing frequency number, in which the word <can> is classified as the IP class, to 3.075 which is greater than 30 by 2.5%.

In another example, the processor 260 may increase the oversampling rate only when the IP frequency number of the word is greater than the non-IP frequency number of the word.

In contrast, the processor 260 may not perform oversampling of the word when the IP frequency number of the word is less than the non-IP frequency number of the word. That is, the processor 260 may fix the oversampling rate when the IP frequency number of the word is less than the non-IP frequency number of the word.

FIG. 11 is a view illustrating an oversampling rate determined according to a ratio of a non-IP frequency number to an IP frequency number.

FIG. 11 shows the oversampling rate determined according to the ratio of the non-IP frequency number to the IP frequency number of the word of FIG. 10 in the 10000 sentences stored in the database 232.

That is, FIG. 11 shows the non-IP frequency number in which each word is not classified as the IP class, the IP frequency number in which each word is classified as the IP class, the relative ratio of non-IP frequency number to the IP frequency number, and the oversampling rate determined according to the relative ratio.

As can be seen from FIG. 11, as the relative ratio increases, the oversampling rate increases. As the relative ratio decreases, the oversampling rate decreases.

When the oversampling rate increases, a probability that the word is classified as the IP class may increase.

When the probability that the word is classified as the IP class increases, the class imbalance can be solved and the reading break performance of the synthesized speech model may increase.

FIG. 9 will be described again.

The processor 260 of the speech synthesis server 30 determines the number of times of oversampling of the word using the determined oversampling rate (S903).

In one embodiment, the number of times of oversampling of the word may indicate the IP frequency number to be increased based on the determined oversampling rate of the word.

The IP frequency number to be increased may indicate the number of sentences including the word classified as the IP class.

That is, increasing the number of times of oversampling of the word may indicate that the number of sentences including the word classified as the IP class increases.

In one embodiment, the processor 260 may determine the number of times of oversampling of the word based on the oversampling rate determined in step S901.

In another embodiment, the processor 260 may determine the number of times of oversampling the word, based on the oversampling rate, the number of words classified as the major class in the database 232, the number of words classified as the minor class, the number of times of labeling the word with the minor class, a probability that the word belongs to the minor class, and the number of times in which the word appears in the database 232.

Specifically, the processor 260 may determine the number of times of oversampling as shown in Equation 1 below.

$\begin{matrix} {{word}_{i:{over}} = {{SamplingRate}*\frac{{Class}_{Major}}{{Class}_{minor}}*{{{word}_{i} = {minor}}}*{P\left( {word}_{i:{minor}} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack \end{matrix}$

where, word_(i) may indicate a specific word present in the database 232,

word_(i:over) may indicate the number of times of oversampling of word_(i),

Sampling Rate may be a constant determined in step S901 and may have a value of 10% to 100%, but this is merely an example,

|Class_(Major)| may indicate the number of words in the major class,

|Class_(Minor)| may indicate the number of words in the minor class, and

P(word_(i=minor)) may indicate a probability that a specific word belongs to the minor class.

P(word_(i=minor)) may be expressed by Equation 2 below.

$\begin{matrix} \frac{{{word}_{i} = {minor}}}{{word}_{i}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack \end{matrix}$

where, |Word_(i=minor)| may indicate the number of times in which word_(i) is labeled with the minor class in the database 232.

Labeling the word with the minor class may mean that words <government's>, <year>, <rain> and <Monday> which are used as criteria used to determine the count of the IP class which is the minor class are classed into the IP class, in FIGS. 6 and 7.

|word_(i)| may indicate the number of times in which word_(i) appears in the database 232.

That is, |word_(i)| may indicate the number of times in which word_(i) appears in a plurality of sentences of the database 232.

The processor 260 of the speech synthesis server 30 stores the determined number of times of oversampling in the database 232 (S905).

The processor 260 may generate sentences including the words, the number of which correspond to the determined number of times of oversampling the word.

The processor 260 may label the word with the IP class and generate sentences including the word labeled with reading break of 3 such that the number of sentences corresponds to the number of times of oversampling.

The processor 260 may learn the synthesized speech model using the sentences including the word and the labeling data of labeling the word with reading break.

FIG. 12 is a ladder diagram illustrating a method of operating a system according to an embodiment of the present invention.

Referring to FIG. 12, the speech synthesis server 30 acquires sentences including the word classified as the IP class by the number of times of oversampling of the word (S1201).

The speech synthesis server 30 may generate arbitrary sentences including the word.

The arbitrary sentences may be training data for learning of the synthesized speech model.

The speech synthesis server 30 learns the synthesized speech model using the acquired sentences (S1203).

The word classified as the IP class may be labeled with reading break of 3.

The speech synthesis server 30 may learn the synthesized speech model using the arbitrary sentences (training data) and the labeling data of labeling the word in the arbitrary sentences with the reading break.

In one embodiment, the processor 260 of the speech synthesis server 30 may learn the synthesized speech model using a recurrent neural network (RNN).

The recurrent neural network is a kind of artificial neural network in which a hidden layer is connected to a directional edge to form a recurrent structure.

A process of learning the synthesized speech model using the recurrent neural network will be described with reference to FIG. 13.

FIG. 13 is a view illustrating a basic structure of a recurrent neural network.

Xt denotes input data, Ht denotes current hidden data, H(t−1) denotes previous hidden data, and Yt denotes output data.

The input data, the hidden data and the output data may be expressed by feature vectors.

Parameters learned by the RNN include a first parameter W1 for converting the previous hidden data into the current hidden data, a second parameter W2 for converting the input data into the hidden data and a third parameter W3 for converting the current hidden data into the output data.

The first, second and third parameters W1, W2 and W3 may be expressed by a matrix.

According to the present invention, the input data may be a feature vector indicating a word, and the output data may be a feature vector indicating a first probability that an input word belongs to a WP class, a second probability that the input word belongs to an AP class and a third probability that the input word belongs to an IP class.

The previous hidden data may be hidden data of a previously input word, and the current hidden data may be data generated using the hidden data of the previously input word and a feature vector of a currently input word.

FIG. 14 is a view illustrating a process of classifying words configuring a sentence into classes using a synthesized speech model according to an embodiment of the present invention.

Referring to FIG. 14, a plurality of words 1310 configuring one sentence is sequentially input to the synthesized speech model 1330.

The terminal 100 or the speech synthesis server 30 may output a first probability (1351) that each of the sequentially input words 1310 is classified as the WP class, a second probability (1353) that each of the sequentially input words 1310 is classified as the AP class and a third probability (1355) that each of the sequentially input words 1310 is classified as the IP class, using the synthesized speech model 1330.

The terminal 100 or the speech synthesis server 30 may classify a probability having the largest value among the first to third probabilities into the class of the input word.

FIG. 12 will be described again.

The speech synthesis server 30 transmits the learned synthesized speech model to the terminal 100 (S1205).

The terminal 100 outputs the synthesized speech according to the request of the user through the audio output unit 152 using the synthesized speech model received from the speech synthesis server 30 (S1207).

The request of the user may be the speech command of the user, such as <Read news article>.

The terminal 100 may receive the speech command of the user and grasp the intention of the received speech command.

The terminal 100 may output, through the audio output unit 152, the synthesized speech of the text corresponding to the news article suiting the grasped intention using the synthesized speech model.

FIG. 15 is a flowchart illustrating a method of operating a speech synthesis server using artificial intelligence according to another embodiment of the present invention.

Referring to FIG. 15, the processor 260 of the speech synthesis server 30 acquires prior information of each of a plurality of words corresponding to a minor class (S1501).

Hereinafter, assume that the minor class is the intonation phrase class of FIG. 7.

A word belonging to (or being classified as) the intonation phrase class means that a word located before <//> indicating reading break of 3, such as <government's> shown in FIG. 6, belongs to the intonation phrase class.

In one embodiment, the prior information may include one or more of an intonation phrase (hereinafter referred to as IP) ratio of a word, an IP frequency number, a non-IP ratio in which the word does not belong to the intonation phrase class (hereinafter referred to as a non-IP ratio), a non-IP frequency number, or a ratio of the non-IP frequency number to the IP frequency number.

The IP ratio may indicate a ratio in which a word is classified as the IP class, in the database 232. Specifically, in 10000 sentences in the database 232, when the number of times of classifying a first word into an IP class is 100, the IP ratio of the first word may be 1%(100/10000×100).

FIG. 16 is a diagram illustrating prior information of each word stored in a database according to an embodiment of the present invention.

FIG. 16 shows an IP table 1600 showing an IP ratio in which each word is classified as the IP class and a non-IP ratio in which each word is not classified as the IP class.

The IP table 1600 shows the IP ratio which is the ratio in which each word is classified as the IP class in the sentences stored in the database 232 and the non-IP ratio obtained by subtracting the IP ratio from 1, with respect to each of the plurality of words.

The non-IP ratio may be a sum of the ratio in which the word is classified as the WP class and the ratio in which the word is classified as the AP class.

For example, the IP ratio of the word “Because” is 0.84 and the non-IP ratio thereof is 0.16 (1−0.84).

In addition, the IP ratio of the word “This” is 0.15 and the non-IP ratio thereof is 0.85.

FIG. 15 will be described again.

The processor 260 of the speech synthesis server 30 acquires a first class classification probability set indicating the per-class classification probability of each word used as labeling data of the synthesized speech model (S1503).

The synthesized speech model may be an artificial neural network based model learned by a machine learning algorithm or a deep learning algorithm.

For example, the synthesized speech model may be a recurrent neural network based model shown in FIG. 13.

The first class classification probability set may include a probability that the word is classified as the WP class, a probability that the word is classified as the AP class and a probability that the word is classified as the IP class, within one sentence.

Specifically, a first probability that the word is classified as the WP class may indicate a probability of reading a word with break of 1 within one sentence.

Similarly, a second probability that the word is classified as the AP class may indicate a probability of reading a word with break of 2 within one sentence, and a third probability that the word is classified as the IP class may indicate a probability of reading a word with break of 3 within one sentence.

The processor 260 may infer a probability that each word is classified as the WP class, a probability that each word is classified as the AP class and a probability that each word is classified as the IP class, using the synthesized speech model.

The synthesized speech model may be a model composed of an artificial neural network learned to infer a first class classification probability set indicating the output feature point using a sentence including a plurality of words as input data.

For example, the synthesized speech model may be learned through supervised learning. Specifically, learning data used for the synthesized speech model may be labeled with the probability that the word is classified as the WP class, the probability that the word is classified as the AP class and the probability that the word is classified as the IP class.

The synthesized speech model may be learned using the labeled learning data.

The synthesized speech model may be learned with the goal of accurately inferring the probability that the word included in text data is classified as the labeled WP class, the probability that the word included in text data is classified as the AP class and the probability that the word included in text data is classified as the IP class, from text data for learning.

The weighted cost function of the synthesized speech model may be expressed by a squared mean of a difference between each class probability corresponding to each learning data and each class probability inferred from learning data.

Through learning of the synthesized speech model, model parameters included in the artificial neural network may be determined to minimize the value of the weighted cost function.

FIG. 17 is a diagram illustrating an example of a synthesized speech model according to an embodiment of the present invention.

Referring to FIG. 17, a synthesized speech model 1700 composed of an artificial neural network is shown.

Text data which is learning data and a per-class probability which is labeling data may be input to the synthesized speech model 1700 as one training set.

As a result of inference, the per-class probability may be output.

The synthesized speech model 1700 may be learned to minimize the cost function corresponding to a difference between the output per-class probability and the labeled per-class probability.

The synthesized speech model 1700 may be learned, such that a result of inferring each per-class classification probability is output as a target feature vector and a cost function corresponding to a difference between the output per-class classification probability set and the labeled per-class classification probability set is minimized, when an input feature vector is extracted from the text data including words and input to the synthesized speech model.

The output result of the synthesized speech model 1700 may be composed of an output layer having a plurality of output nodes indicating the per-class classification probability of the word.

Each of the plurality of output nodes may indicate the probability that the word is classified as the WP class, the probability that the word is classified as the AP class and the probability that the word is classified as the IP class.

Each of the plurality of output nodes may be expressed by a target feature vector such as (0.3, 0.3, 0.4). Each of the values of the elements configuring the target feature vector may have a value of 0 to 1.

FIG. 15 will be described again.

The processor 260 of the speech synthesis server 30 acquires a second class classification probability set indicating a corrected per-class classification probability of each word based on the prior information and first class classification probability set of each word (S1505).

The processor 260 may correct the first class classification probability set to the second class classification probability set, based on the IP ratio and the first class classification probability set of the word.

The processor 260 may adjust the class classification probability set to be used as labeling data in the synthesized speech model 1700, based on the IP ratio and the first class classification probability set of the word.

This is because labeling data is corrected by applying the IP ratio in which a specific word belongs to the IP class and a non-IP ratio in which the specific word belongs to the non-IP ratio in the plurality of sentences stored in the database.

When labeling data, to which the IP ratio and the non-IP ratio are applied, is used to learn the synthesized speech model, since the distribution of the word classified as the IP class is applied, it is possible to improve class classification accuracy.

Therefore, it is possible to solve a class imbalance problem.

A process of correcting the first class classification probability set in consideration of the IP ratio and the non-IP ratio of the word will be described with reference to the following drawings.

FIGS. 18 to 21 are diagrams illustrating an example of correcting a class classification probability set in consideration of an IP ratio and a non-IP ratio of a word according to an embodiment of the present invention.

First, FIGS. 18 and 19 will be described based on the word <Because>.

In addition, for the IP ratio of the word <Because>, refer to the IP table 1600 of FIG. 16.

Referring to FIG. 18, the first class classification probability set 1800 which is labeling data corresponding to the word <Because> is shown.

As the labeling data of <Because>, a probability that the word is classified as the WP class is 0.3, a probability that the word is classified as the AP class is 0.6, and a probability that the word is classified as the IP class is 0.1.

In FIG. 18, each of the probability that the word is classified as the WP class, the probability that the word is classified as the AP class and the probability that the word is classified as the IP class may be a mathematical probability.

The processor 260 may acquire the second class classification probability set 1900 shown in FIG. 19, based on the IP ratio, non-IP ratio and first class classification probability set 1800 of <Because>.

The corrected WP class classification probability may be expressed as shown in Equation 3 below. Corrected WP class classification probability=(WP class classification probability before correction)*(Non-IP ratio)*(probability that the word is classified as the WP class/probability that the word is not classified as the IP class)  [Equation 3]

Accordingly, a value of 0.3*0.16*(0.3/0.9)=0.016 may be obtained as the corrected WP class classification probability by Equation 3.

The corrected AP class classification probability may be expressed by Equation 4 below. Corrected AP class classification probability=(AP class classification probability before correction)*(Non-IP ratio)*(probability that the word is classified as the AP class/probability that the word is not classified as the IP class)  [Equation 4]

Accordingly, a value of 0.6*0.16*(0.6/0.9)=0.064 may be obtained as the corrected AP class classification probability by Equation 4.

The corrected IP class classification probability may be expressed by Equation 5 below. Corrected IP class classification probability=(IP class classification probability before correction)*(IP ratio)  [Equation 5]

Accordingly, a value of 0.1*0.84=0.084 may be obtained as the corrected IP class classification probability by Equation 5.

Meanwhile, the processor 260 may change each of the corrected class classification probabilities to a normalized value based on 1.

The probability that the word <Because> is classified as the corrected WP class is 0.97, the probability that the word <Because> is classified as the corrected AP class is 0.390, and the probability that the word <Because> is classified as the corrected IP class is 0.513.

That is, the first class classification probability set (0.3, 0.6, 0.1) may be changed to the second class classification probability set (0.097, 0.390, 0.513).

That is, the WP class classification probability decreased from 0.3 to 0.097, the AP class classification probability decreased from 0.6 to 0.390, and the IP class classification probability decreased from 0.1 to 0.513.

The processor 260 may increase the probability that the word is classified as the IP class as the IP ratio of the word increases and decreases the probability that the word is classified as the IP class as the IP ratio decreases.

The probability that the word is classified as the IP class may increase by correcting the labeling data in consideration of the IP ratio of the word stored in the database 232.

Therefore, when the synthesized speech is generated, a possibility that the word belongs to the IP class increases, thereby solving class imbalance.

Next, FIGS. 20 and 21 will be described.

FIGS. 20 and 21 will be described based on the word <This>.

In addition, for the IP ratio of the word <This>, refer to the IP table 1600 of FIG. 16.

Referring to FIG. 20, the first class classification probability set 2000 which is labeling data corresponding to the word <This> is shown.

As the labeling data of <This>, a probability that the word is classified as the WP class is 0.3, a probability that the word is classified as the AP class is 0.3, and a probability that the word is classified as the IP class is 0.4.

The processor 260 may acquire the second class classification probability set 2100 shown in FIG. 21, based on the IP ratio, non-IP ratio and first class classification probability set 2000 of <This>.

The corrected WP class classification probability may be expressed as shown in Equation 3 above.

A value of 0.3*0.85*(0.3/0.6)=0.127 may be obtained as the corrected WP class classification probability by Equation 3.

The corrected AP class classification probability may be expressed by Equation 4 above.

A value of 0.3*0.85*(0.3/0.6)=0.127 may be obtained as the corrected AP class classification probability by Equation 4.

The corrected IP class classification probability may be expressed by Equation 5 above.

A value of 0.4*0.15=0.06 may be obtained as the corrected IP class classification probability by Equation 5.

Meanwhile, the processor 260 may change each of the corrected class classification probabilities to a normalized value based on 1.

The probability that the word <This> is classified as the corrected WP class is 0.4, the probability that the word <This> is classified as the corrected AP class is 0.4, and the probability that the word <This> is classified as the corrected IP class is 0.2.

That is, the first class classification probability set (0.3, 0.3, 0.4) may be changed to the second class classification probability set (0.4, 0.4, 0.2).

That is, the WP class classification probability increased from 0.3 to 0.4, the AP class classification probability increased from 0.3 to 0.4, and the IP class classification probability decreased from 0.4 to 0.2.

The probability that the word is classified as the IP class may decrease by correcting the labeling data in consideration of the IP ratio of the word stored in the database 232.

Therefore, when the synthesized speech is generated, a possibility that the word belongs to the IP class decreases, thereby solving class imbalance.

That is, according to the embodiment of the present invention, it is possible to improve reading break prediction performance of the synthesized speech model.

FIG. 15 will be described again.

The processor 260 of the speech synthesis server 30 or the learning processor 240 learns the synthesized speech model using the acquired second class classification probability set (S1507).

The processor 260 may learn the synthesized speech model using the acquired second class classification probability set as new labeling data.

A process of learning the synthesized speech model using the second class classification probability set will be described with reference to FIG. 22.

FIG. 22 is a diagram illustrating a process of learning a synthesized speech model using a newly acquired second class classification probability set based on an IP ratio according to an embodiment of the present invention.

Referring to FIG. 22, a training set including text data including words and class classification probability set of each word may be input to the synthesized speech model 1700.

The synthesized speech model 1700 may output a first class classification probability set 2210 including a probability that each word is classified as the WP class, a probability that each word is classified as the AP class and a probability that each word is classified as the IP class, with respect to the training set.

The processor 260 may acquire a second class classification probability set 2230 based on the output first class classification probability set 2210 and the IP ratio and non-IP ratio of each word.

That is, the processor 260 may perform probability correction operation to change the first class classification probability set 2210 to the second class classification probability set 2230, as shown in FIGS. 18 to 21.

The processor 260 may use the newly acquired second class classification probability set 2230 as new labeling data of the synthesized speech model 1700.

Meanwhile, the synthesized speech models described with reference to FIGS. 15 to 22 may be transmitted to the terminal.

The terminal may obtain the per-class classification probability of each word included in text data corresponding to a sentence using the synthesized speech mode.

FIG. 23 is a ladder diagram illustrating a method of operating another system of the present invention.

In particular, FIG. 23 relates to a method of outputting a synthesized speech in consideration of a reading-with-break style of a user.

The processor 260 of the speech synthesizer 30 acquires an IP ratio table of each of a plurality of voice actors based on the plurality of voice actors stored in the database 232 (S2301).

The database 232 stores speech data uttered by each of the plurality of voice actors.

The processor 260 may acquire the IP ratio table based on the speech data uttered by each voice actor. The IP ratio table may include an IP ratio in which the plurality of words is classified as an IP class and a non-IP ratio which the plurality of words is not classified as an IP class.

This will be described with reference to FIG. 24.

FIG. 24 is a view illustrating a plurality of IP tables respectively corresponding to a plurality of voice actors according to an embodiment of the present invention.

The processor 260 may acquire the IP ratio of each word based on the speech data corresponding to the speech uttered by each voice actor.

Each of the plurality of voice actors 2401 to 2403 may utter words with different breaks according to the unique utterance style thereof, even if the words are the same.

Referring to FIG. 24, a first IP ratio table 2410 obtained based on the speech uttered by the first voice actor 2401, a second IP ratio table 2430 obtained based on the speech uttered by a second voice actor 2403 and a third IP table 2450 obtained based on the speech uttered by a third voice actor 2405 are shown.

The first IP ratio table 2410 includes an IP ratio in which the first voice actor 2401 reads each of a plurality of words with break corresponding to the IP class and a non-IP ratio in which the first voice actor 2401 reads each of a plurality of words with break corresponding to the non-IP class.

The second IP ratio table 2430 includes an IP ratio in which the second voice actor 2403 reads each of a plurality of words with break corresponding to the IP class and a non-IP ratio in which the first voice actor 2403 reads each of a plurality of words with break corresponding to the non-IP class.

The second IP ratio table 2450 includes an IP ratio in which the second voice actor 2405 reads each of a plurality of words with break corresponding to the IP class and a non-IP ratio in which the first voice actor 2405 reads each of a plurality of words with break corresponding to the non-IP class.

In FIG. 24, the IP ratio tables of three voice actors are described but this is merely an example and IP ratio tables of more voice actors may be obtained.

FIG. 23 will be described.

The processor 260 of the speech synthesizer 30 acquires a normal IP ratio table indicating a normal IP ratio of each word using the plurality of acquired IP ratio tables (S2303).

The processor 260 may calculate an average of the IP ratios of each word included in each of the plurality of IP ratio tables.

For example, when the IP ratios of three voice actors for each word are a1, a2 and a3, the normal IP ratio may be (a1+a2+a3)/3.

This will be described with reference to FIG. 25.

FIG. 25 is a view illustrating a normal IP ratio table according to an embodiment of the present invention.

FIG. 24 is used to describe FIG. 25.

Referring to FIG. 25, the normal IP ratio table 2500 is shown.

The IP ratio of each word included in the normal IP ratio table 2500 may be obtained by the average of the IP ratios of each word included in each of the IP ratio tables shown in FIG. 24.

For example, the normal IP ratio of a word <Because> will be described.

The IP ratio of <Because> is 0.84 in the first IP ratio table 2410, is 0.80 in the second IP ratio table 2430, and is 0.70 in the third IP ratio table 2450.

The normal IP ratio of <Because> is 0.780, by calculating (0.84+0.80+0.70)/3.

The normal non-IP ratio of <Because> may be obtained by subtracting the normal IP ratio from 1.

In this manner, the normal IP ratio of each of the plurality of words may be calculated and the normal IP ratio table 2500 which is a combination of the normal IP ratios may be obtained.

As described below, the normal IP ratio table 2500 may be used to train the normal synthesized speech model.

FIG. 23 will be described again.

The processor 260 of the speech synthesizer 30 generates a normal synthesized speech model based on the acquired normal IP ratio table (S2305).

The normal synthesized speech model may be a model for determining a probability that a word is classified as an IP class, a probability that a word is classified as a WP class and a probability that a word is classified as an AP class, using the normal IP ratio of each word included in the normal IP ratio table.

After the normal synthesized speech model is trained, the reading break of the word may be determined according to the class having the highest probability among the determined probabilities when the synthesized speech is generated.

The normal synthesized speech model may be an artificial neural network based model learned by a deep learning algorithm or a machine learning algorithm.

The normal synthesized speech model may be learned through supervised learning.

Learning data used for the normal synthesized speech model may include text data corresponding to a sentence including a plurality of words, a normal IP ratio of each of the plurality of words, and an IP class classification probability labeled with each word.

Detailed description of the normal synthesized speech model may be replaced with the embodiment of FIG. 17.

The processor 260 of the speech synthesizer 30 transmits the generated normal synthesized speech model to the terminal 100 through the communication unit 210 (S2307).

The terminal 100 stores the normal synthesized speech model received from the speech synthesizer 30 in the memory 170 and collect utterance information of the user (S2309).

The terminal 100 may output a speech based on the normal synthesized speech model.

The terminal 100 may receive the speech data uttered by the user and acquire an intention of the received speech data.

The terminal 100 may acquire text corresponding to the acquired intention and output a synthesized speech corresponding to the acquired text using the normal synthesized speech model. The terminal 100 may output the synthesized speech, to which the reading break of each word included in the synthesized speech is applied.

The terminal 100 may collect utterance information based on the speech data uttered by the user.

The utterance information may include the number of times of reading words configuring a sentence uttered by the user in the IP class, the part of speech of the word, and the position of the word in the sentence.

The processor 260 of the speech synthesizer 30 receives the utterance information of the user collected by the terminal 100 through the communication unit 210 (S2311).

The processor 260 may use the received utterance information to acquire a personalized IP ratio table.

The personalized IP ratio table may be data used to train the personalized synthesized speech model. The personalized IP ratio table may include IP ratios of each word applied to a specific person.

The processor 260 of the speech synthesizer 30 acquires the utterance IP ratio of each of a plurality of uttered words based on the received utterance information of the user (S2313).

The utterance IP ratio may be an IP ratio correspond to each of the plurality of words uttered by the user.

The utterance IP ratio may be a ratio in which the words uttered by the user are read with break corresponding to the IP class.

The processor 260 may change the normal IP ratio of each word used in the normal synthesized speech model to a newly acquired utterance IP ratio.

This will be described with reference to FIG. 26.

FIG. 26 is a view illustrating a table including personalized IP ratios and normal IP ratios of acquired words based on utterance information of a user.

Referring to FIG. 26, a table 2600 includes a normal IP ratio 2610 and a personalized IP ratio 2630 of each of a plurality of words.

For example, the normal IP ratio of a word <Because> obtained based on utterance of the plurality of voice actors may be 0.78 and the personalized IP ratio of the word <Because> obtained based on utterance of a specific person may be 0.75.

For example, the personalized IP ratio may be obtained through the number of times that the user reads the word <Because> included in 100 sentences with break corresponding to the IP class.

In addition, the normal IP ratio of a word <For> obtained based on utterance of the plurality of voice actors may be 0.697 and the personalized IP ratio of the word <For> obtained based on utterance of a specific person may be 0.65.

That is, the IP ratio may be changed to generate the personalized synthesized speech model.

The personalized synthesized speech model may be a personalized model for outputting a synthesized speech, to which the reading-with-break style of the user is applied.

The personalized synthesized speech model may be a model for outputting a synthesized speech optimized for the user who receives the speech recognition service through the terminal 100.

Meanwhile, the collected utterance information of the user requires personalized IP ratios of words unuttered by the user.

That is, referring to FIG. 26, words <We>, <And> and <This> are unuttered by the user and thus the personalized IP ratios thereof may not be directly calculated.

To this end, the processor 260 may estimate the normal IP ratios of the unuttered words.

FIG. 24 will be described again.

The processor 260 of the speech synthesizer 30 estimates the non-utterance IP ratios respectively corresponding to the unuttered words based on the utterance information and the acquired utterance IP ratios (S2315).

The utterance information may include the part of speech of the word uttered by the user, the length of the uttered sentence and the position of the uttered word in the sentence.

The processor 260 may estimate the non-utterance IP ratios of the unuttered words based on the utterance information and the personalized IP ratios of the uttered words.

The processor 260 may determine the IP ratio of the unuttered word based on the IP ratio model.

The IP ratio model may be a model for determining a probability that the unuttered word is classified as an IP class, using the unuttered word, the property of the unuttered word, an IP ratio of the uttered word having a property similar to that of the unuttered word, and labeling data (a probability of being classified as the IP class).

The uttered word having the property similar to that of the unuttered word may be a word similar to the unuttered word.

The processor 260 may determine the probability that the word is classified as the IP class as the IP ratio of the unuttered word.

This will be described with reference to FIG. 27.

FIG. 27 is a view illustrating an IP ratio model according to an embodiment of the present invention.

The IP ratio model 2700 may be a model for estimating the IP ratio of a word unuttered by the user.

The IP ratio model may be an artificial neural network based model learned by a deep learning algorithm or a machine learning algorithm.

Learning data used to train the IP ratio model may include an unuttered word, a property of the unuttered word, and labeling data (a probability of being classified as the IP class).

The property of the unuttered word may include one or more of the part of speech of the unuttered word or the position of the unuttered word in the sentence.

The IP ratio model 2700 may be a model for accurately inferring the probability that the unuttered word is classified as the IP class, using, as input data, an unuttered word, a property of the unuttered word, and the probability that the word is classified as the IP class.

The labeling data may be a personalized IP ratio of an uttered word having the same part of speech as an unuttered word and having a position in the sentence similar to that of the unuttered word.

The processor 260 may acquire the personalized IP ratio of the word unuttered by the user using the IP ratio model 2700.

FIG. 28 is a view illustrating a result of estimating personalized IP ratios of words unuttered by a user according to an embodiment of the present invention.

Referring to the table 2800 of FIG. 28, personalized IP ratios 2810 (non-utterance IP ratios) of the words <We>, <And> and <This> unuttered by the user, which are estimated using the IP ratio model 2700, may be included.

The personalized IP ratios respectively corresponding to the words unuttered by the user may be used to train the personalized synthesized speech model.

FIG. 23 will be described again.

The processor 260 of the speech synthesizer 30 generates a personalized synthesized speech model based on the utterance IP ratios and the estimated non-utterance IP ratios (S2317).

The processor 260 may generate the personalized synthesized speech model based on the IP ratios of the uttered words and the non-utterance IP ratios.

The personalized synthesized speech model may be a model for outputting the synthesized speech, to which the reading-with-break style of the user is applied.

The method of training the personalized synthesized speech model may be equal to the method of training the synthesized speech model shown in FIG. 17. However, as the IP ratios used as the learning data, the personalized IP ratios shown in FIG. 28 may be used.

The personalized synthesized speech model may be an artificial neural network based model learned by a deep learning algorithm or a machine learning algorithm.

The processor 260 may apply the oversampling scheme described with reference to FIGS. 8 and 9 to the personalized synthesized speech model, in order to increase reading break prediction performance.

In another example, the processor 260 may apply the embodiment of FIG. 15 to the personalized synthesized speech model in order to increase reading break prediction performance.

The processor 260 of the speech synthesizer 30 transmits the personalized synthesized speech model to the terminal 100 through the communication unit 210 (S2319).

The terminal 100 may store the personalized synthesized speech model in the memory 170.

The terminal 100 may output the synthesized speech suiting the reading-with-break style of the user when the speech recognition service is provided to the user.

Therefore, the user can listen to the speech suiting the utterance style thereof, thereby greatly improving satisfaction with the speech recognition service.

Meanwhile, when utterance information of words unuttered by the user are collected, the processor 260 may update the personalized synthesized speech model.

This will be described with reference to FIG. 29.

FIG. 29 is a flowchart illustrating a process of updating a personalized synthesized speech model at a speech synthesizer according to an embodiment of the present invention.

Referring to FIG. 29, the processor 260 of the speech synthesizer 30 collects the utterance information of the unuttered word (S2901).

The processor 260 may receive the utterance information of the unuttered word from the terminal 100.

The utterance information of the unuttered word may include the number of times of reading a word in the IP class, the part of speech of the word, and the position of the word in the sentence.

The processor 260 of the speech synthesizer 30 acquires the IP ratio of the unuttered word based on the collected utterance information of the unuttered word (S2903).

The processor 260 may acquire the IP ratio based on the number of times of reading the unuttered word in the IP class.

The processor 260 of the speech synthesizer 30 determines whether a difference between the acquired IP ratio and the IP ratio estimated in step S2315 is equal to or greater than a predetermined ratio (S2905).

The predetermined ratio may be 0.05 but this is merely an example.

The processor 260 of the speech synthesizer 30 retrains the personalized synthesized speech model when the difference between the acquired IP ratio and the estimated IP ratio is equal to or greater than the predetermined ratio, in order to accurately generate the personalized synthesized speech model (S2907).

When the difference between the acquired IP ratio and the estimated IP ratio is large, the processor 260 may retrain the personalized synthesized speech model in order to accurately generate the personalized synthesized speech model.

That is, the processor 260 may train the personalized synthesized speech model by changing the estimated IP ratio of the unuttered word to the IP ratio of the newly uttered word.

The processor 260 of the speech synthesizer 30 acquires the personalized synthesized speech model updated by retraining and transmits the updated personalized synthesized speech model to the terminal 100 (S2909).

The terminal 100 may store the updated personalized synthesized speech model in the memory 170 and provide the speech service through the updated personalized synthesized speech model.

Therefore, it is possible to provide the synthesized speech, to which the reading-with-break style of the user is applied, thereby greatly improving user's satisfaction with the speech recognition service.

The present invention mentioned in the foregoing description can also be embodied as computer readable codes on a computer-readable recording medium. Examples of possible computer-readable mediums include HDD (Hard Disk Drive), SSD (Solid State Disk), SDD (Silicon Disk Drive), ROM, RAM, CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, etc. The computer may include the processor 180 of the terminal. 

What is claimed is:
 1. A speech synthesizer using artificial intelligence, comprising: a memory; a communication unit configured to receive utterance information of words uttered by a user from a terminal; and a processor configured to acquire a plurality of utterance intonation phrase (IP) ratios respectively corresponding to a plurality of words uttered by the user based on the utterance information, acquire a plurality of non-utterance IP ratios respectively corresponding to a plurality of unuttered words based on the utterance information and the plurality of utterance IP ratios, and generate a personalized synthesized speech model based on the plurality of utterance IP ratios and the plurality of non-utterance IP ratios, wherein the personalized synthesized speech model is a model for outputting a synthesized speech, to which reading break of words uttered by the user is applied, and is an artificial neural network based model learned by a deep learning algorithm or a machine learning algorithm, wherein a plurality of classes indicating reading break of a word includes a first class corresponding to first reading break, a second class corresponding to second reading break greater than the first reading break and a third class corresponding to third reading break greater than the second reading break, wherein a minor class has a smallest count among the first to third classes, and wherein each of the utterance IP ratios and the non-utterance IP ratios is a ratio in which a word is classified as the minor class.
 2. The speech synthesizer according to claim 1, wherein the utterance information comprises reading break of each uttered word, a part of speech of each uttered word, and a position of each uttered word in a sentence.
 3. The speech synthesizer according to claim 2, wherein the processor is further configured to acquire an utterance IP ratio of each uttered word using a number of times that the user reads each uttered word with break corresponding to the minor class.
 4. The speech synthesizer according to claim 3, wherein the memory stores an IP ratio model for determining an IP ratio of an unuttered word, and wherein the processor is further configured to: determine a probability in which the unuttered word is classified as the minor class, using each unuttered word, a property of each unuttered word, an IP ratio of an uttered word and labeling data, and determine a probability of being classified as a determined IP class as a non-utterance IP ratio of the unuttered word.
 5. The speech synthesizer according to claim 1, wherein the personalized synthesized speech model is a model for inferring a probability that each word is classified as the minor class, using text data corresponding to the plurality of uttered words and the plurality of unuttered words, an IP ratio of each word, and a labeled probability of being classified as the minor class, which is labeled with each word.
 6. The speech synthesizer according to claim 5, wherein the processor is further configured to transmit the personalized synthesized speech model to the terminal through the communication unit.
 7. The speech synthesizer according to claim 1, wherein, when the utterance information of the unuttered words is received, the processor is further configured to acquire the plurality of non-utterance IP ratios using the received utterance information of the unuttered words and to retrain the personalized synthesized speech model using the plurality of acquired unuttered IP ratios.
 8. A method of operating a speech synthesizer using artificial intelligence, the method comprising: receiving, via a communication unit of the speech synthesizer, utterance information of words uttered by a user from a terminal; acquiring, using a processor of the speech synthesizer, a plurality of utterance intonation phrase (IP) ratios respectively corresponding to a plurality of words uttered by the user based on the utterance information; acquiring, using the processor of the speech synthesizer, a plurality of non-utterance IP ratios respectively corresponding to a plurality of unuttered words based on the utterance information and the plurality of utterance IP ratios, generating, using the processor of the speech synthesizer, a personalized synthesized speech model based on the plurality of utterance IP ratios and the plurality of non-utterance IP ratios, wherein the personalized synthesized speech model is a model for outputting a synthesized speech, to which reading break of words uttered by the user is applied, and is an artificial neural network based model learned by a deep learning algorithm or a machine learning algorithm, and outputting, using the processor of the speech synthesizer, a synthesized speech based on an utterance style of the user using the generated personalized synthesized speech model, wherein a plurality of classes indicating reading break of a word includes a first class corresponding to first reading break, a second class corresponding to second reading break greater than the first break and a third class corresponding to third reading break greater than the second break, wherein a minor class has a smallest count among the first to third classes, and wherein each of the utterance IP ratios and the non-utterance IP ratios is a ratio in which a word is classified as the minor class.
 9. The method according to claim 8, wherein the utterance information comprises reading break of each uttered word, a part of speech of each uttered word, and a position of each uttered word in a sentence.
 10. The method according to claim 9, wherein acquiring the plurality of utterance IP ratios further comprises acquiring an utterance IP ratio of each uttered word using a number of times that the user reads each uttered word with break corresponding to the minor class.
 11. The method according to claim 10, further comprising: determining, via the processor of the speech synthesizer, a probability in which the unuttered word is classified as the minor class, using each unuttered word, a property of each unuttered word, an IP ratio of an uttered word and labeling data, and determining, via the processor of the speech synthesizer, a probability of being classified as a determined IP class as a non-utterance IP ratio of the unuttered word.
 12. The method according to claim 8 wherein the personalized synthesized speech model is a model for inferring a probability that each word is classified as the minor class, using text data corresponding to the plurality of uttered words and the plurality of unuttered words, an IP ratio of each word, and a labeled probability of being classified as the minor class, which is labeled with each word.
 13. A non-transitory computer-readable recording medium for performing a method of operating a speech synthesizer using artificial intelligence, the method comprising: receiving utterance information of words uttered by a user from a terminal; acquiring a plurality of utterance intonation phrase (IP) ratios respectively corresponding to a plurality of words uttered by the user based on the utterance information; acquiring a plurality of non-utterance IP ratios respectively corresponding to a plurality of unuttered words based on the utterance information and the plurality of utterance IP ratios, and generating a personalized synthesized speech model based on the plurality of utterance IP ratios and the plurality of non-utterance IP ratios, wherein the personalized synthesized speech model is a model for outputting a synthesized speech, to which reading break of words uttered by the user is applied, and is an artificial neural network based model learned by a deep learning algorithm or a machine learning algorithm, wherein a plurality of classes indicating reading break of a word includes a first class corresponding to first reading break, a second class corresponding to second reading break greater than the first break and a third class corresponding to third reading break greater than the second break, wherein a minor class has a smallest count among the first to third classes, and wherein each of the utterance IP ratios and the non-utterance IP ratios is a ratio in which a word is classified as the minor class. 